Thunderspiking
Thunderspiking is a technique that Pikachu and Pichu can use by launching an opponent upwards (usually from an up smash or an up tilt) and using Thunder to Star KO them when they are near the upper blast line, allowing them to score a vertical KO at a rather low damage percentage. This technique is often used as a combo finisher (notably at the end of Isai's Greenhouse combo), or just for KOing. In Smash 64, the tornado hazard on Hyrule Castle can be used by Pikachu players to set up a Thunderspike, due to its high vertical knockback.
In Super Smash Bros., Thunderspiking is very effective, as Thunder has infinite vertical range, making it easier for Pikachu to get KOs by around 20%-30% less than just an up smash itself. However, it is harder to pull the technique off in Super Smash Bros. Melee, as Thunder now strikes from a cloud at a fixed height (though it's still rather high), the falling speeds of characters are in general faster, and the move is slower and more laggy. In Super Smash Bros. Brawl, Thunderspiking is more effective than in Melee and it is possible to combo into it with an up tilt at much lower percentages than in the previous two games, but opponents can air dodge without becoming helpless (allowing them to dodge the bolt), hindering its effectiveness.
